is it possible to ALTER a PRIMARY KEY CLUSTERED Index on an existing table without losing the data?
If so, what is the ALTER command for this please?
EDIT
I want to add an additional column to the PRIMARY KEY CLUSTERED Index
Thanks
Here is what I've done in the past to change a primary key on a table:
BEGIN TRANSACTION doStuff
DECLARE #isValid bit
SET #isValid = 1
DECLARE #pkName varchar(50)
SET #pkName = (
SELECT TOP 1 name
FROM sys.key_constraints
WHERE type ='pk'
AND OBJECT_NAME(parent_object_id) = N'TableName'
)
DECLARE #sql nvarchar(2000)
SET #sql = N'
ALTER TABLE dbo.TableName
DROP CONSTRAINT ' + #pkName
EXEC (#sql)
IF (##ERROR <> 0)
BEGIN
PRINT 'Error deleting primary key'
SET #isValid = 0
END
ALTER TABLE dbo.TableName
ADD PRIMARY KEY (primary key columns separated by comma)
IF (##ERROR <> 0)
BEGIN
PRINT 'Error creating primary key'
SET #isValid = 0
END
IF (#isValid = 1)
BEGIN
PRINT 'Commit'
COMMIT TRANSACTION doStuff
END
ELSE
BEGIN
PRINT 'Rollback'
ROLLBACK TRANSACTION doStuff
END
Note as pointed out in: Best way to change clustered index (PK) in SQL 2005 this will reorder the data in your table throughout the operation, so depending on the size of the table it could take a significant amount of time.
Related
I have a Firebird table like this:
CREATE TABLE events (
event VARCHAR(6) NOT NULL
CHECK (event IN ('deploy', 'revert', 'fail')),
change_id CHAR(40) NOT NULL,
change VARCHAR(512) NOT NULL
);
Now I need to add another value to the IN() list in the CHECK constraint. How do I do that?
Things I've tried so far:
Updating the value in RDB$TRIGGERS.RDB$TRIGGER_SOURCE:
UPDATE RDB$TRIGGERS
SET RDB$TRIGGER_SOURCE = 'CHECK (event IN (''deploy'', ''revert'', ''fail'', ''merge''))'
WHERE RDB$TRIGGER_SOURCE = 'CHECK (event IN (''deploy'', ''revert'', ''fail''))';
Does not seem to work, as the trigger is compiled in RDB$TRIGGERS.RDB$TRIGGER_BLR.
Creating a new table with a new check, copying the data over, dropping the old table and renaming the new table. However, it seems that one cannot rename a Firebird table, so I can't make the new table have the same name as the old one.
I suspect updating RDB$TRIGGERS is the way to go (idk!), if only I could get Firebird to recompile the code. But maybe there's a better way?
You need to drop and the re-create the check constraint.
As you didn't specify a name for your constraint, Firebird created one, so you first need to find that name:
select trim(cc.rdb$constraint_name), trg.rdb$trigger_source
from rdb$relation_constraints rc
join rdb$check_constraints cc on rc.rdb$constraint_name = cc.rdb$constraint_name
join rdb$triggers trg on cc.rdb$trigger_name = trg.rdb$trigger_name
where rc.rdb$relation_name = 'EVENTS'
and rc.rdb$constraint_type = 'CHECK'
and trg.rdb$trigger_type = 1;
I just added the trigger source for informational reasons.
Once you have the name, you can drop it, e.g.
alter table events drop constraint integ_27;
and then add the new constraint:
alter table events
add constraint check_event_type
CHECK (event IN ('deploy', 'revert', 'fail', 'merge'));
In the future you don't need to look for the constraint name because you already it.
Here's how to do it dynamically:
SET AUTOddl OFF;
SET TERM ^;
EXECUTE BLOCK AS
DECLARE trig VARCHAR(64);
BEGIN
SELECT TRIM(cc.rdb$constraint_name)
FROM rdb$relation_constraints rc
JOIN rdb$check_constraints cc ON rc.rdb$constraint_name = cc.rdb$constraint_name
JOIN rdb$triggers trg ON cc.rdb$trigger_name = trg.rdb$trigger_name
WHERE rc.rdb$relation_name = 'EVENTS'
AND rc.rdb$constraint_type = 'CHECK'
AND trg.rdb$trigger_type = 1
INTO trig;
EXECUTE STATEMENT 'ALTER TABLE EVENTS DROP CONSTRAINT ' || trig;
END^
SET TERM ;^
COMMIT;
ALTER TABLE events ADD CONSTRAINT check_event_type CHECK (
event IN ('deploy', 'revert', 'fail', 'merge')
);
COMMIT;
I had to disable AUTOddl and put in explicit commits or else I got a deadlock on the ALTER TABLE ADD CONSTRAINT statement.
Here's how to do it dynamically:
EXECUTE BLOCK RETURNS (STMT VARCHAR(1000)) AS
BEGIN
SELECT TRIM(R.RDB$CONSTRAINT_NAME)
FROM RDB$RELATION_CONSTRAINTS R
WHERE R.RDB$RELATION_NAME = 'TABLE_NAME'
AND UPPER(R.RDB$CONSTRAINT_TYPE) = UPPER('PRIMARY KEY')
INTO :STMT;
IF (:STMT IS NOT NULL) THEN
BEGIN
EXECUTE STATEMENT 'ALTER TABLE TABLE_NAME DROP CONSTRAINT ' || :STMT || ';';
EXECUTE STATEMENT 'ALTER TABLE TABLE_NAME ADD CONSTRAINT ' || :STMT || ' PRIMARY KEY (FIELD1, FIELD2, FIELD3);';
END
ELSE
BEGIN
EXECUTE STATEMENT 'ALTER TABLE FIELD1 ADD CONSTRAINT PK_PRIMARY_NAME PRIMARY KEY (FIELD1, FIELD2, FIELD3);';
END
END;
I have to remove this constraint on the TYPE_FR column from an existing table but this one does not have a constraint name and the examples I find need the name of the constraint that this one does not have. Thank you
TYPE_FR INTEGER NOT NULL CHECK (TYPE_FR > 0 AND TYPE_FR < 3)
Db2 will generate an anonymous (system generated) name for the constraint if you don't explicitly name the constraint.
You can find the system generated name in the catalog tables/views.
For Db2-on-Linux/Unix/Windows, here is one way to do it, example below.
If your Db2-server is Db2-for-Z/OS, then use sysibm.syschecks2.checkname to find the constraint name to drop.
If your Db2-server is Db2-for-i (as/400), then use qsys2.syschkcst.constraint_name to find the constraint name to drop.
create table MY_TEST_TABLE (TYPE_FR INTEGER NOT NULL CHECK (TYPE_FR > 0 AND TYPE_FR < 3) )
DB20000I The SQL command completed successfully.
select constname from syscat.colchecks where tabschema='USER1' and tabname = 'MY_TEST_TABLE'
CONSTNAME
--------------------------------------------------------------------------------------------------------------------------------
SQL210205171553170
1 record(s) selected.
begin
declare constraint_name varchar(128);
declare my_sql varchar(1024);
set constraint_name = (select constname
from syscat.colchecks
where tabschema='USER1'
and tabname = 'MY_TEST_TABLE'
);
if constraint_name is not null then
set my_sql = 'alter table MY_TEST_TABLE drop constraint '||constraint_name ;
execute immediate my_sql ;
end if;
end
DB20000I The SQL command completed successfully.
select constname from syscat.colchecks where tabschema='USER1' and tabname = 'MY_TEST_TABLE'
CONSTNAME
--------------------------------------------------------------------------------------------------------------------------------
0 record(s) selected.
I'm using PostgreSQL 8.1.23 on x86_64-redhat-linux-gnu
I have to write a database for reserving seats on language courses and there's a requirement there should be a trigger, which will check whether lector, we're trying to write into new group, has any other group at the same time. I have such table:
CREATE TABLE groups (
group_id serial PRIMARY KEY,
lang varchar(3) NOT NULL,
level varchar(3),
seats int4,
lector int4,
start time,
day varchar(3),
FOREIGN KEY (language) REFERENCES languages(lang) ON UPDATE CASCADE ON DELETE CASCADE,
FOREIGN KEY (lector) REFERENCES lectors(lector_id) ON UPDATE CASCADE ON DELETE SET NULL);
and such trigger:
CREATE FUNCTION if_available () RETURNS trigger AS '
DECLARE
r groups%rowtype;
c groups%rowtype;
BEGIN
FOR r IN SELECT * FROM groups WHERE r.lector=NEW.lector ORDER BY group_id LOOP
IF (r.start = NEW.start AND r.day = NEW.day) THEN
RAISE NOTICE ''Lector already has a group at this time!'';
c = NULL;
EXIT;
ELSE
c = NEW;
END IF;
END LOOP;
RETURN c;
END;
' LANGUAGE 'plpgsql';
CREATE TRIGGER if_available_t
BEFORE INSERT OR UPDATE ON grupy
FOR EACH ROW EXECUTE PROCEDURE if_available();
After inserting the new row to a table groups, eg.:
INSERT groups (lang, level, seats, lector, start, day) values ('ger','A-2',12,2,'11:45','wed');
I get an error like this:
ERROR: null value in column "group_id" violates not-null constraint
Without this trigger everything is OK. Could anybody help me how to make it work?
Finally, I have solved it! After BEGIN there should be c = NEW;, because when table groups is empty at the beginning, FOR loop doesn't run and NULL is returned. Also I have changed the condition in FOR loop for: ...WHERE lector = NEW.lector.... And finally, I have changed the condition in IF for IF (r.group_id <> NEW.group_id AND r.start = NEW.start AND r.day = NEW.day) THEN..., because I haven't wanted to run this trigger before one particular update. Maybe this will be helpful for someone :)
This is my table :
CREATE TABLE [dbo].[TestTable]
(
[Name1] varchar(50) COLLATE French_CI_AS NOT NULL,
[Name2] varchar(255) COLLATE French_CI_AS NULL,
CONSTRAINT [TestTable_uniqueName1] UNIQUE ([Name1]),
CONSTRAINT [TestTable_uniqueName1Name2] UNIQUE ([Name1], [Name2])
)
ALTER TABLE [dbo].[TestTable]
ADD CONSTRAINT [TestTable_uniqueName1]
UNIQUE NONCLUSTERED ([Name1])
ALTER TABLE [dbo].[TestTable]
ADD CONSTRAINT [TestTable_uniqueName1Name2]
UNIQUE NONCLUSTERED ([Name1], [Name2])
GO
ALTER INDEX [TestTable_uniqueName1]
ON [dbo].[TestTable]
DISABLE
GO
My idea is to enable/disable one or other unique contraint depending on the customer application. With this way, I can catch the thrown exception in my c# code, and display a specific error message to the GUI.
Now, my problem is to alter the collation of columns Name1 & Name2, I need to make them case sensitive (French_CS_AS). To alter these fields, I have to drop the two constraints and recreate it. According to the explained schema, I cannot create an enabled constraint and then disable it, because by some customers, I have duplicate keys for one or other constraint.
For my update script, my idea number 1 was
Save the name of enabled constraints in a temp table
Drop the constraints
Alter columns
Create DISABLED unique constraints
Enable specific constraints according to the saved values in points 1.
My problem is in point 4., I don't find how to create a disabled unique constraint with an ALTER TABLE statement. Is it possible to create it directly in the sys.indexes table ?
My idea number 2 was
Rename TestTable to TestTableCopy
Recreate TestTable with the new fields collation, and otherwise the same schema (indexes, FK, triggers, ...)
Disable specifical unique contraints in TestTable
Migrate data from TestTableCopy to TestTable
Drop TestTableCopy
In this way, my fear is to loose some links with other tables/dependencies, beceause it is a central table in my database.
Is there any other way to achieve my goal?
If necessary, I can use unique indexes instead of unique constraints.
It looks like it is impossible to create a unique index on a column that already has duplicate values.
So, rather than having a disabled unique index either:
not have an index at all (which is the same as having a disabled index from the query processor point of view),
or create a non-unique index.
For those instanses where your client has unique data create unique index. For those instanses where your client has non-unique data create non-unique index.
CREATE PROCEDURE [dbo].[spUsers_AddUsers]
#Name1 varchar(50) ,
#Name2 varchar(50) ,
#Unique bit
AS
declare #err int
begin tran
if #Unique = 1 begin
if not exists (SELECT * FROM Users WHERE Name1 = #Name1 and Name2 = #Name2)
begin
INSERT INTO Users (Name1,Name2)
VALUES (#Name1,#Name2)
set #err = ##ERROR
end else
begin
UPDATE Users
set Name1 = #Name1,
Name2 = #Name2
where Name1 = #Name1 and Name2 = #Name2
set #err = ##ERROR
end
end else begin
if not exists ( SELECT * FROM Users WHERE Name1 = #Name1 )
begin
INSERT INTO Users (Name1,Name2)
VALUES (#Name1,#Name2)
set #err = ##ERROR
end else
begin
UPDATE Users
set Name1 = #Name1,
Name2 = #Name2
where Name1 = #Name1
set #err = ##ERROR
end
if #err = 0 commit tran
else rollback tran
So first you check if you need an unique Name1 and Name2 or just Name1. Then if you do you an insert/update based on what constrain you have.
Is there a way to change existing primary key type from int to serial without dropping the table? I already have a lot of data in the table and I don't want to delete it.
Converting an int to a serial more or less only means adding a sequence default to the value, so to make it a serial;
Pick a starting value for the serial, greater than any existing value in the table
SELECT MAX(id)+1 FROM mytable
Create a sequence for the serial (tablename_columnname_seq is a good name)
CREATE SEQUENCE test_id_seq MINVALUE 3 (assuming you want to start at 3)
Alter the default of the column to use the sequence
ALTER TABLE test ALTER id SET DEFAULT nextval('test_id_seq')
Alter the sequence to be owned by the table/column;
ALTER SEQUENCE test_id_seq OWNED BY test.id
A very simple SQLfiddle demo.
And as always, make a habit of running a full backup before running altering SQL queries from random people on the Internet ;-)
-- temp schema for testing
-- ----------------------------
DROP SCHEMA tmp CASCADE;
CREATE SCHEMA tmp ;
SET search_path=tmp;
CREATE TABLE bagger
( id INTEGER NOT NULL PRIMARY KEY
, tralala varchar
);
INSERT INTO bagger(id,tralala)
SELECT gs, 'zzz_' || gs::text
FROM generate_series(1,100) gs
;
DELETE FROM bagger WHERE random() <0.9;
-- SELECT * FROM bagger;
-- CREATE A sequence and tie it to bagger.id
-- -------------------------------------------
CREATE SEQUENCE bagger_id_seq;
ALTER TABLE bagger
ALTER COLUMN id SET NOT NULL
, ALTER COLUMN id SET DEFAULT nextval('player_id_seq')
;
ALTER SEQUENCE bagger_id_seq
OWNED BY bagger.id
;
SELECT setval('bagger_id_seq', MAX(ba.id))
FROM bagger ba
;
-- Check the result
-- ------------------
SELECT * FROM bagger;
\d bagger
\d bagger_id_seq